linux-kernel - [PATCH v5 13/22] perf jevents: Add context switch metrics for Intel

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Message-ID: <20250829041104.4186320-14-irogers@google.com>
Date: Thu, 28 Aug 2025 21:10:54 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Xu Yang <xu.yang_2@....com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, John Garry <john.g.garry@...cle.com>, 
	Jing Zhang <renyu.zj@...ux.alibaba.com>, Sandipan Das <sandipan.das@....com>, 
	Benjamin Gray <bgray@...ux.ibm.com>, Perry Taylor <perry.taylor@...el.com>, 
	Samantha Alt <samantha.alt@...el.com>, Caleb Biggers <caleb.biggers@...el.com>, 
	Weilin Wang <weilin.wang@...el.com>, Edward Baker <edward.baker@...el.com>, 
	Thomas Falcon <thomas.falcon@...el.com>
Subject: [PATCH v5 13/22] perf jevents: Add context switch metrics for Intel

Metrics break down context switches for different kinds of
instruction.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/pmu-events/intel_metrics.py | 55 ++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/tools/perf/pmu-events/intel_metrics.py b/tools/perf/pmu-events/intel_metrics.py
index df0e1dce041c..31ef0373d982 100755
--- a/tools/perf/pmu-events/intel_metrics.py
+++ b/tools/perf/pmu-events/intel_metrics.py
@@ -262,6 +262,60 @@ def IntelBr():
                      description="breakdown of retired branch instructions")
 
 
+def IntelCtxSw() -> MetricGroup:
+  cs = Event("context\-switches")
+  metrics = [
+      Metric("lpm_cs_rate", "Context switches per second", d_ratio(cs, interval_sec), "ctxsw/s")
+  ]
+
+  ev = Event("instructions")
+  metrics.append(Metric("lpm_cs_instr", "Instructions per context switch",
+                        d_ratio(ev, cs), "instr/cs"))
+
+  ev = Event("cycles")
+  metrics.append(Metric("lpm_cs_cycles", "Cycles per context switch",
+                        d_ratio(ev, cs), "cycles/cs"))
+
+  try:
+    ev = Event("MEM_INST_RETIRED.ALL_LOADS", "MEM_UOPS_RETIRED.ALL_LOADS")
+    metrics.append(Metric("lpm_cs_loads", "Loads per context switch",
+                          d_ratio(ev, cs), "loads/cs"))
+  except:
+    pass
+
+  try:
+    ev = Event("MEM_INST_RETIRED.ALL_STORES", "MEM_UOPS_RETIRED.ALL_STORES")
+    metrics.append(Metric("lpm_cs_stores", "Stores per context switch",
+                          d_ratio(ev, cs), "stores/cs"))
+  except:
+    pass
+
+  try:
+    ev = Event("BR_INST_RETIRED.NEAR_TAKEN", "BR_INST_RETIRED.TAKEN_JCC")
+    metrics.append(Metric("lpm_cs_br_taken", "Branches taken per context switch",
+                          d_ratio(ev, cs), "br_taken/cs"))
+  except:
+    pass
+
+  try:
+    l2_misses = (Event("L2_RQSTS.DEMAND_DATA_RD_MISS") +
+                 Event("L2_RQSTS.RFO_MISS") +
+                 Event("L2_RQSTS.CODE_RD_MISS"))
+    try:
+      l2_misses += Event("L2_RQSTS.HWPF_MISS", "L2_RQSTS.L2_PF_MISS", "L2_RQSTS.PF_MISS")
+    except:
+      pass
+
+    metrics.append(Metric("lpm_cs_l2_misses", "L2 misses per context switch",
+                          d_ratio(l2_misses, cs), "l2_misses/cs"))
+  except:
+    pass
+
+  return MetricGroup("lpm_cs", metrics,
+                     description = ("Number of context switches per second, instructions "
+                                    "retired & core cycles between context switches"))
+
+
 def IntelIlp() -> MetricGroup:
   tsc = Event("msr/tsc/")
   c0 = Event("msr/mperf/")
@@ -671,6 +725,7 @@ def main() -> None:
       Smi(),
       Tsx(),
       IntelBr(),
+      IntelCtxSw(),
       IntelIlp(),
       IntelL2(),
       IntelLdSt(),
-- 
2.51.0.318.gd7df087d1a-goog